Rolling metal strips from metal particles



United States Patent 3,493,368 ROLLING METAL STRIPS FROM METAL PARTICLES Eckard Gehring, Dusseldorf-Kaiserswerth, Germany, as-

signor to Schloemann Aktiengesellschaft, Dusseldorf, Germany, a company of Germany No Drawing. Filed Aug. 28, 1967, Ser. No. 663,544 Claims priority, application Germany, Sept. 6, 1966, Sch 39,496 Int. Cl. B22f 3/18 US. Cl. 75-222 3 Claims ABSTRACT OF THE DISCLOSURE A method of rolling metal strips (particularly aluminum strips) of different thicknesses from metal particles of different sizes, the sizes of the particles employed being varied according to the thickness of the sheets to be produced, with rolls of a given diameter.

The space filling (ratio of bulk density of the particles to the density of the metal of which they consist) may also be taken into consideration.

This invention relates to a method of rolling metal strips of different thicknesses from metal particles. In this connection the surprising discovery has been made that a high-grade strip can be obtained, under substantially more favourable rolling conditions than hitherto, if, according to this invention, the particle size of the metal granules is so selected that coarse-grained particles are used for the production of thick strips and fine-grained particles for the production of thin strips. With metal particles of the same bulk density, their particle size may be chosen directly proportional to the thickness of the strip to be produced.

This method has the further advantage that such metal particles as accrue in production in different particles sizes can be advantageously allocated to particular uses according to their size. Above all, even the grit and powder portion, from granules for example, is thus rendered available for deformation.

According to a further feature of the invention, the thin and thick strips can be produced on a rolling mill with rolls of the same diameter, particularly with rolls of small diameter. This result is the more noteworthy, because hitherto the view has been held that for the consolidation of metal particles, proportionality must be maintained between the roll diameters and the thickness of the strip to be rolled. For relatively thick strips, therefore, one was bound to use rolls of considerable diameter, which led not only to comparatively expensive roll stands, but also, on account of the increased length pressed, involved greater roll forces and greater torques. The strip produced according to the invention also accrues in this case with a high press density.

A further improvement in the method proposed is arrived at when one also takes into consideration the spacefilling of the particles. The space-filling here is the ratio of the bulk density of the particles to the density of the metal of which they consist. This is taken into consideration by multiplying the space-filling by the mean size of the particles, and choosing particles in which this product is proportional to the thickness of the strip to be produced.

It is particularly advantageous to roll the metal particles at a temperature which lies above the recrystallisation 3,493,368 Patented Feb. 3, 1970 temperature of the metal of which they consist. One thereby obtains a texture of such density that the strips assume even the full theoretical density of the metal in question. With metals which at this temperature tend to form disturbing oxide coatings, it is advisable to effect the deformation under protective gas, in order to ensure the welding of the particles into a compact product.

From this invention it is therefore clear that the size of the particles, their space-filling, and the diameters of the rolls, are interchangeable with one another, in order to arrive at a strip of a definite thickness. The space filling is indeed bound up with the shape and size of the particles, but the particle size, and the diameters of the rolls, admit of being freely chosen. This relationship is expressed in the following equation:

mean particle size (mm.) space fillingX roll diameter (mm.)

thickness of strip (mm.)

The numerical value of this expression, in which the dimensions are expressed in millimetres, and the space filling is dimensionless, is frequently constant for a definite metal. For aluminum, for example, it amounts to between 220 and 235. It is obvious also to adopt as a basis a corresponding relationship for other metals, allowing in certain cases for the coeflicient of friction. It is however to be taken into consideration here that with elongated particles their mean length is to be regarded as the mean size of the particles.

The invention will now be further elucidated with reference to a specific example:

From an aluminum melt containing 99.5% aluminum, granules were produced, which were worked up into strips between two rolls arranged with their axes horizontal. For this purpose the granules were heated to 450 C., and supplied, freely flowing, by way of a funnel or hopper, to the roll gap of the rolling mill. The diameters of the rolls here were 350 mm. As particles, there were employed a grit with a mean particle size of 3 mm., and granules with a mean particle size of 8 mm. The test results are set forth hereunder:

size bulk density.

In both cases, at the first passage through the rolling mill, an aluminum strip was obtained with practically the density of cast aluminum. The special advantage consisted in the fact that one did not have to change the rolls, the same rolls being employed for the strip thicknesses in the ratio of 1:5.

The method according to the invention is not limited in its adoption to the range of magnitudes given by way of comparison in the example, or to the ratio of magnitudes there indicated, but may also advantageously be adopted with greater deviations of the corresponding numerical values, and with essentially all metals.

I claim:

1. A method of producing aluminum strips of different thicknesses from aluminum particles of different sizes and space filling consisting in the steps of dividing said aluminum particles into at least relatively coarse and fine divisions, said coarse division being used for producing thick strips and said fine division being used for producing thin strips; rolling said divisions of particles at elevated temperatures into their respective strip thicknesses; and maintaining the value of the following relationship:

mean particle size (mm.) space filling roll diameter (mm.)

thickness of the strip (mm) References Cited UNITED STATES PATENTS 5/1956 Naeser 75208 XR 6/1959 H. Evans et a1. 75-214 2,987,778 6/1961 Worn 75-214 XR 3,290,145 12/1966 Daugherty 75214 3,359,100 12/1967 Claus 75-214 FOREIGN PATENTS 714,927 9/ 1954 Great Britain.

776,544 6/1957 Great Britain.

796,220 6/1958 Great Britain.

825,953 12/1959 Great Britain.

OTHER REFERENCES The Compaction of Metal Powders by Rolling. IThe Properties of Strip Rolled From Copper Powders, P. E. Evans, and G. C. Smith, Powder Metallurgy, 1959, No. 3. pp. 115.

CARL D. QUARFORTH, Primary Examiner A. J. STEINER, Assistant Examiner 

